content: /* Copyright (C) 2016-2018 Alibaba Group Holding Limited
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import static com.google.protobuf.Internal.checkNotNull;
  
  import com.google.protobuf.Internal.EnumLite;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Internal representation of map fields in generated lite-runtime messages.
   *
   * This class is a protobuf implementation detail. Users shouldn't use this
   * class directly.
   */
  public final class MapFieldLite<K, V> extends LinkedHashMap<K, V> {
  
    private boolean isMutable;
  
    private MapFieldLite() {
      this.isMutable = true;
    }
  
    private MapFieldLite(Map<K, V> mapData) {
      super(mapData);
      this.isMutable = true;
    }
  
    @SuppressWarnings({"rawtypes", "unchecked"})
    private static final MapFieldLite EMPTY_MAP_FIELD = new MapFieldLite();
    static {
      EMPTY_MAP_FIELD.makeImmutable();
    }
  
    /** Returns an singleton immutable empty MapFieldLite instance. */
    @SuppressWarnings({"unchecked", "cast"})
    public static <K, V> MapFieldLite<K, V> emptyMapField() {
      return (MapFieldLite<K, V>) EMPTY_MAP_FIELD;
    }
  
    public void mergeFrom(MapFieldLite<K, V> other) {
      ensureMutable();
      if (!other.isEmpty()) {
        putAll(other);
      }
    }
  
    @SuppressWarnings({"unchecked", "cast"})
    @Override public Set<Map.Entry<K, V>> entrySet() {
      return isEmpty() ? Collections.<Map.Entry<K, V>>emptySet() : super.entrySet();
    }
  
    @Override public void clear() {
      ensureMutable();
      super.clear();
    }
  
    @Override public V put(K key, V value) {
      ensureMutable();
      checkNotNull(key);
  
      checkNotNull(value);
      return super.put(key, value);
    }
  
    public V put(Map.Entry<K, V> entry) {
      return put(entry.getKey(), entry.getValue());
    }
  
    @Override public void putAll(Map<? extends K, ? extends V> m) {
      ensureMutable();
      checkForNullKeysAndValues(m);
      super.putAll(m);
    }
  
    @Override public V remove(Object key) {
      ensureMutable();
      return super.remove(key);
    }
  
    private static void checkForNullKeysAndValues(Map<?, ?> m) {
      for (Object key : m.keySet()) {
        checkNotNull(key);
        checkNotNull(m.get(key));
      }
    }
  
    private static boolean equals(Object a, Object b) {
      if (a instanceof byte[] && b instanceof byte[]) {
        return Arrays.equals((byte[]) a, (byte[]) b);
      }
      return a.equals(b);
    }
  
    /**
     * Checks whether two {@link Map}s are equal. We don't use the default equals
     * method of {@link Map} because it compares by identity not by content for
     * byte arrays.
     */
    static <K, V> boolean equals(Map<K, V> a, Map<K, V> b) {
      if (a == b) {
        return true;
      }
      if (a.size() != b.size()) {
        return false;
      }
      for (Map.Entry<K, V> entry : a.entrySet()) {
        if (!b.containsKey(entry.getKey())) {
          return false;
        }
        if (!equals(entry.getValue(), b.get(entry.getKey()))) {
          return false;
        }
      }
      return true;
    }
  
    /**
     * Checks whether two map fields are equal.
     */
    @SuppressWarnings("unchecked")
    @Override
    public boolean equals(Object object) {
      return (object instanceof Map) && equals(this, (Map<K, V>) object);
    }
  
    private static int calculateHashCodeForObject(Object a) {
      if (a instanceof byte[]) {
        return Internal.hashCode((byte[]) a);
      }
      // Enums should be stored as integers internally.
      if (a instanceof EnumLite) {
        throw new UnsupportedOperationException();
      }
      return a.hashCode();
    }
  
    /**
     * Calculates the hash code for a {@link Map}. We don't use the default hash
     * code method of {@link Map} because for byte arrays and protobuf enums it
     * use {@link Object#hashCode()}.
     */
    static <K, V> int calculateHashCodeForMap(Map<K, V> a) {
      int result = 0;
      for (Map.Entry<K, V> entry : a.entrySet()) {
        result += calculateHashCodeForObject(entry.getKey())
            ^ calculateHashCodeForObject(entry.getValue());
      }
      return result;
    }
  
    @Override
    public int hashCode() {
      return calculateHashCodeForMap(this);
    }
  
    private static Object copy(Object object) {
      if (object instanceof byte[]) {
        byte[] data = (byte[]) object;
        return Arrays.copyOf(data, data.length);
      }
      return object;
    }
  
    /**
     * Makes a deep copy of a {@link Map}. Immutable objects in the map will be
     * shared (e.g., integers, strings, immutable messages) and mutable ones will
     * have a copy (e.g., byte arrays, mutable messages).
     */
    @SuppressWarnings("unchecked")
    static <K, V> Map<K, V> copy(Map<K, V> map) {
      Map<K, V> result = new LinkedHashMap<K, V>();
      for (Map.Entry<K, V> entry : map.entrySet()) {
        result.put(entry.getKey(), (V) copy(entry.getValue()));
      }
      return result;
    }
  
    /** Returns a deep copy of this map field. */
    public MapFieldLite<K, V> mutableCopy() {
      return isEmpty() ? new MapFieldLite<K, V>() : new MapFieldLite<K, V>(this);
    }
  
    /**
     * Makes this field immutable. All subsequent modifications will throw an
     * {@link UnsupportedOperationException}.
     */
    public void makeImmutable() {
      isMutable = false;
    }
  
    /**
     * Returns whether this field can be modified.
     */
    public boolean isMutable() {
      return isMutable;
    }
  
    private void ensureMutable() {
      if (!isMutable()) {
        throw new UnsupportedOperationException();
      }
    }
  }
  